a. Field of the Invention
The present invention pertains to electronic amplifier circuits and specifically to integrated circuit amplifier circuits.
b. Description of the Background
Amplifier circuits are used in may applications in integrated circuits. One common amplifier circuit is a cascode current mirror that is commonly used in integrated circuits. In general, the current mirrors are designed to generate a flat output. That is, the gain is constant throughout the frequency operating range.
In some applications, there is need to increase or decrease the output of an amplifier in selective portions of the frequency range. For example, if an amplifier receives a signal from a device that has a gain that changes with frequency, the signal would need to be amplified so that the resultant gain was constant over the frequency range.
It would therefore be advantageous to provide an amplifier circuit wherein a current signal may be amplified by different gains over different frequency ranges.
The present invention overcomes the disadvantages and limitations of the prior art by providing a system and method for amplifying a current signal on an integrated circuit wherein a variable resistor is placed between the input line and the gate of a first transistor of a cascode amplifier and a variable capacitance may further be introduced to change the gain of the signal at different frequencies. Additionally, several transistors may be switched in or out of the circuitry to adjust the gain in the lower regions of input frequencies. The variable resistance, variable capacitance, and switchable transistors can be used to adjust the gain of the amplifier over different frequencies.
The present invention may therefore comprise an equalizing current amplifier comprising: an input line; an output line; a first set of input transistors connected in parallel having the drains connected to the input line and the sources connected to ground, the first set of input transistors comprising at least one transistor; a variable resistor connected to the input line and the gates of the first set of input transistors; and a first set of output transistors connected in parallel having the gates connected to the input line, the sources connected to ground, and the drains connected to the output line, the first set of output transistors comprising at least one transistor.
The present invention may further comprise an equalizing current amplifier comprising: an input line; an output line; a first set of input transistors connected in parallel having the drains connected to the input line, the gates connected to the input line, and the sources connected to ground, the first set of input transistors comprising at least one transistor, a variable capacitor connected to the gates of the first set of input transistors and ground; and a first set of output transistors connected in parallel having the gates connected to the input line, the sources connected to ground, and the drains connected to the output line, the first set of output transistors comprising at least one transistor.
The present invention may further comprise an equalizing current amplifier comprising: an input line; an output line; a first set of input transistors connected in parallel having the drains connected to the input line and the sources connected to ground, the first set of input transistors comprising at least one transistor; a resistor connected to the input line and the gates of the first set of input transistors; a second set of input transistors connected in parallel having the drains connected to the input line, the gates connected to the gates of the first set of input transistors, and the sources connected to a switch, the switch being connected to ground, the second set of input transistors comprising at least one transistor; and a first set of output transistors connected in parallel having the gates connected to the input line, the sources connected to ground, and the drains connected to the output line, the first set of output transistors comprising at least one transistor.
The advantages of the present invention are that current signals may be amplified with a tunable boost across a specific frequency range. The circuitry required is simple and therefore takes up a small portion of space on an integrated circuit. The signal boost may be tuned to a specific frequency range depending on the resistor value or capacitance value chosen. Further, the gain at lower frequencies may be adjusted by switching additional transistors in and out of the circuit.